This invention relates to a type of mountaineering hardware often referred to as a "chock", "chockstone", "nut", or by the more generic term "artificial chockstone".
The term "nut" derives from the original artificial chockstones which were, in fact, nothing more than machine nuts which had their internal threads removed or covered over. One or more of these nuts were strung on a loop of rope and gained widespread popularity in the early 1950's through the mid-1960's as mountaineering hardware.
The names "chock" and "artificial chockstone" derive from the still earlier climbing practice of "tying-off" chockstones, a chockstone being a natural rock, block, or stone found jammed or wedged in a crack. To "tie-off" a chockstone is a broad term meaning to tie, in some manner, a rope, sling, cable or webbing around, through, over, behind, or onto a chockstone. The "tied" (a term which includes knots, compression sleeves, and sewn splices) rope, sling, cable or webbing is often referred to as a "tie-off" or a "runner". Basically then, a chock, or an artificial chockstone, is a man-made chockstone-like object tied-off, or suitable for tying-off, with a runner. For simplicity, the artificial chockstones comprising this invention will be referred to hereinafter merely as "chocks".
The basic use for chocks is to secure, through suitable placement, a point of attachment in a crack in a rock formation. The four principal reasons for obtaining such points of attachment are for belaying, anchoring, rappelling and direct aid climbing. These four uses are not totally distinct and under some circumstances overlaps do occur, as for example, when direct aid placements are also relied on for protection in belaying. Nonetheless, the foregoing distinctions constitute readily distinguishable reasons for the chock's usage even if more than one reason might be applicable for a particular chock placement.
The basic modus operandi of chocks in each of the aforementioned uses is the same. The chock is placed in a crack beyond a constriction such that the chock jams, wedges, or otherwise becomes lodged at the constriction when pulled toward the constriction. Of course, in order to achieve this, the crack and the chock must be compatible, that is, the chock must be small enough to fit in the crack, but not so small so as to slip by the constriction while at the same time, the chock's runner must be capable of passing through or around the constriction.
Generally, there are five major considerations in the placement of a chock: (1) the ultimate force the chock may be required to hold; (2) the speed and ease with which the chock may be placed; (3) the position or location of the placement; (4) the direction or directions from which a pull might be exerted on the chock; and (5) the capability of the chock to remain securely placed. The difference in emphasis in these placement considerations can result in an ideal placement of a chock for one of the aforementioned uses to be unacceptable for one or more of the other usages. All five of these placement considerations are affected to some extent by the design of the chock as will become more fully apparent in the discussion presented hereinafter.
In describing a chock, those surfaces which are intended to jam against the supporting rock formation are referred to as "working surfaces". Generally, working surfaces exist as pairs of opposed surfaces. In addition, chocks have top and bottom surfaces. The bottom surface is generally that surface from which the runner typically depends and which faces in the general direction in which the runner is expected to be pulled. It is obvious that with some chock designs capable of being placed in one of several distinct orientations, the surfaces defined as the working surfaces and the bottom surface become a function of the particular orientation under consideration. Nonetheless, with respect to a particular placement, the working surfaces and the bottom surface of the chock are always readily identifiable. The top surface of the chock is that surface which is on proximately the opposite side from the bottom surface. Depending on the particular design, intervening corners may or may not clearly demarcate the varying chock surfaces. In either case, the respective surfaces are functionally distinct when in use.
In practice, the chock is usually placed "on the run" with one hand while hanging on with the other hand, or while precariously balancing on a ledge. Accordingly, it is obvious that, to the extent to which it is practicable, the chock should be uncomplicated, easily placed, and suitable to varying cracks while at the same time it must be both light weight and as strong as is consistent with its size, material, and other design criteria.
A serious problem with all chocks is the persistent tendency of the belay rope to dislodge the chock as the climber continues to climb on above his chock placement. Often the chock is tapped on the top, usually with an alpine hammer, in order to secure a snug setting and thereby minimize this problem. While this practice can be helpful at times, it has the following serious drawbacks: tapping the chock is not consistently successful in preventing the chock's accidental dislodgement; tapping requires that the climber carry a tapping means, usually an alpine hammer; tapping makes removal of the chock difficult; tapping can damage the runner; abrasion caused as a result of tapping is the primary cause of chock degregation; and, in cases where the crack is of insufficient size or of unfavorable geometry, tapping can become awkward or even infeasible. As will become evident, prominent features of my chock invention are directed towards the elimination of these problems.
Typically, most prior art chocks have been either cut from conventional hexagonal bar-stock thus emulating the original "nuts", or cut from other bar-stock usually more or less round in cross section. These chocks have drilled through them, in a direction generally perpendicular to the length of the bar-stock, two apertures through which the runner is passed. Thus the runner is passed from the bottom surface up through the first aperture over the top surface and then back down through the second aperture to the bottom surface where the ends are joined thereby forming a loop. As a result of passing over the top surface of the chock, in those cases where the chock is tapped as is a common practice, interference from the runner renders the tapping ineffective and in addition the runner is always in jeopardy of being damaged. Additionally as a result of the runner egressing through two distinct and separate apertures at the bottom surface, placements requiring that the two depending portions of the runner be in contact at their egress from the chock, so as to permit their passage through a narrow constriction, are prevented.
A feature of some prior art chocks has been the addition of lightening apertures which are drilled either transversely or lengthwise through the bar-stock to reduce the weight of the chock. More recently, special bar-stock possessing the lightening apertures as an integral part has been specifically extruded for the manufacture of chocks. In addition, changes in the shape of the two tie-off apertures have been tried in an effort to better accommodate the flat webbing currently in use as runners. Nonetheless, all of these chocks are in essence the same as those described heretofore and suffer the same inherent deficiencies.
Another common prior art chock is one fashioned in the general form of a truncated four-sided pyramid where the smaller, truncated end forms the bottom and the two pairs of opposed trapezoidal faces form the working surfaces. As with the aforementioned bar-stock chocks, two apertures connecting the bottom and the top surfaces are provided through which the runner passes up, over the top surface, and back down through the bottom. As is obvious, such a chock and runner system possess those same deficiencies as heretofore described with respect to the runner system in the bar-stock chocks.
Some prior art chocks have a tie-off aperture running from end to end (in bar-stock type chocks) or from side to side (in the truncated pyramid type chocks). These tie-off apertures are essentially the same as the apertures through the original "nuts", however, some have been modified by the addition of slots extending from the ends of the apertures down to the bottom surface. This modification permits the chock to be wedged against the faces in which the apertures are located without pinching the runner. However, in order for this to be accomplished, both ends of the runner have to be successfully held in their slots during the placement of the chock. The problem associated with keeping the runner in its proper place during placement is a major drawback of this design. Some of these chocks having the general form of a truncated pyramid have been further modified by having their top and bottom surfaces oriented so that they form a third taper. In practice, chocks of this particular design have been found to be too complicated to be practicable except in the case of very large sizes.
In order to achieve stronger runners, some chocks, especially in the smaller sizes, have been provided with wire cable runners. Typically, prior art chocks designed for cable runners have two apertures drilled from the top surface down to the bottom surface through which the cable passes up, over the top and back down where the two depending ends are swagged together to form a loop. In this design, the sharp bend which the cable makes as it leaves the top of the apertures critically weakens the cable and the lack of specific provision providing a smoothly arched path in the chock over which the cable can pass is a serious drawback of all prior art chocks having cable runners. In addition, all prior art chocks using cable runners have a single thickness of cable forming the lower loop into which the connecting carabiner is snapped. As a result of the sharp bend in the cable caused by the connecting carabiner, this lower loop of the cable is an additional weak point in this design. Another problem with prior art chocks having cable runners is that when using a rope or webbing runner extension an additional carabiner is required to safely interface the extension to the thin cable runner.
An alternate cable runner design has a single cable depending from the chock and looped back upon itself at the lower end. The single end of the cable passes through an aperture in the bottom of the chock and is retained therein by means of a swagged-on sleeve which is too large to pass back through the aperture. This design typically results in a runner having approximately one-half the strength of the looped cable design described above.
As the size of the crack in a rock formation decreases so does the chock and also the space available for the runner. No prior art chock has provided a runner design for those cases where the crack size is too small to accommodate a cable runner. In the past, pitons rather than chocks have been required for such placements.
Several unique chock designs exist. Two of these designs result from cutting wedge-shaped sections off the end of "I-bar" and "T-bar" extrusions which are subsequently provided with tie-off apertures. These makeshift designs are only suitable to large size chocks. Another design is merely a short cable section with a loop in one end and a compression sleeve forming the chock on the other end. None of these shapes have proved to be particularly suitable for mountain climbing.
A major problem in the design of all prior art chocks is the lack of a specific means for preventing the accidental dislodgement of the chock. Another deficiency in all prior art chocks is the absence of specific provisions for supporting the uppermost edges of the working surfaces of the chock against deformation and/or shear failure. Specific provisions alleviating these two problems as well as other problems described heretofore are prominent features of my chock invention.